The invention relates to a method for the production of a crimped multifilament thread suitable for forming a bulked continuous filament (BCF) a device for the production of a crimped multifilament thread.
In the manufacture of carpeting, for example by tufting or weaving, a so-called bulked continuous filament (BCF) is introduced as a pile thread, which was previously generated in a melt spinning process. In such multifilament threads, it is to be ensured particularly in the further processing that sufficient thread engagement between the filaments of the thread is present. The thread end of the filaments of the thread is ensured in the manufacturing process essentially by a variety of intertwined knots that are generated on the thread before winding the thread. Such intertwined knots are generated by a compressed air treatment of the thread. In order to allow proper processing of the thread to a carpet product, a certain knot stability and a relatively high number of intertwined knots per unit length are desired in the BCF thread.
In the production of a crimped multifilament thread, such intertwined knots are typically generated by swirling the filaments of the thread. Such a method and such a device are described by way of example in EP 0784109 B1. For swirling of the filaments, the thread is passed through a treatment channel of a swirl nozzle, in which a continuous stream of compressed air is directed crosswise to the thread. Depending on the thread guide, the geometric configuration of the treatment channel, and the pressure of the compressed air, intensive swirling is set in motion until the intertwined knots are on the thread. However, the number of interlacing knots per unit length of the thread produced, as well as the knots forming the filaments in the thread due to vibrations of the thread even with constant pressure of the compressed air, is not reproducible. Therefore, the knot stability and the spacing between the intertwined knots more or less depend on the vibrational behavior of the thread and may occur in greater allowances. Such fluctuations in the stability of the intertwined knots and the fluctuation in the number of intertwined knots per unit length of the thread leads to a very differently coloring with the undyed threads depending on the knot stability and number of knots. In the manufacturing of so-called Tricolor colored threads, in which a number of colored filament bundles are spun and subsequently combined to form a crimped thread, irregularities in the formation of the knots and the number of knots lead to undefined visual effects in the subsequent processing of the thread into a carpet material.